Adenovirus vectors

ABSTRACT

An adenoviral vector comprising a promoter further comprising a fragment of the 5′ untranslated region of the CMV IE1 gene including intron A and a nucleic acid sequence encoding a pathogen or tumor antigen for use as a medicament.

The present application is §371 application of PCT/GB2008/001262 filed Apr. 10, 2008 which claims priority to GB Patent Application No. 0706914.9 filed Apr. 10, 2007, the entire disclosure of each being incorporated by reference herein.

FIELD OF THE INVENTION

This invention relates to novel immunogenic adenovirus vector compositions and to their use in immunisation.

BACKGROUND

Vaccination has proved to be one of the most effective means of preventing diseases, particularly infectious diseases. Most vaccines work by inducing antibodies that are protective against infection by the relevant pathogen. However many new vaccines target the cellular arm of the immune system and work by inducing effector and memory T cells. These can target intracellular pathogens and tumours. Many new T cell inducing vaccines that may be used either prophylactically or therapeutically are in development.

T cells induced by vaccination may be useful in various ways. As well as reducing risk of diseases in the vaccinee they may be used in adoptive transfer protocols to reduce risk of infection or disease in those receiving these cells. They may also be useful diagnostically.

An increasingly widely used method of inducing an immune response is to clone an antigen or epitope of interest into a vector. Vectors may be plasmid, bacterial or viral. Plasmid DNA vaccines are under intensive development and a variety of viral vectors appear useful for vaccination. These include poxviruses such as modified vaccinia virus Ankara (MVA), avipox vectors such as fowlpox and canarypox and ALVAC, herpesvirus vectors (including herpes simplex and CMV), alphaviruses and adenoviruses. There is increasing interest in the use of adenoviruses as vaccine vectors because of their ability to induce strong cellular and antibody responses.

Diseases that might be targeted by improved adenovirus vectors include but are not limited to malaria, tuberculosis, HIV/AIDS, HCV, HBV, HSV, HPV, CMV, diseases caused by encapsulated bacteria such as the pneumococcus, parasitic diseases such as leishmaniasis, and a wide range of tumours and cancers, such as lymphoma, leukaemias, melanoma, renal, breast, lung, prostate, pancreatic and colorectal cancers.

SUMMARY OF THE INVENTION

The present invention is based on the inventors surprising discovery that in adenoviral vector vaccines increasing the length of the heterologous promoter which controls expression of the antigen of interest enhances adenoviral vector immunogenicity and protective efficacy.

Adenoviruses form the family Adenoviridae and are classified into five genera (1). First isolated in 1953 from human adenoid tissue removed during tonsillectomy (2), a vast number of species have now been described that are infective to humans and a wide range of animals. All adenoviruses have a similar virion—medium-sized (60-90 nm), non-enveloped, icosahedral particles, with a protein capsid (240 hexons and 12 pentons) enclosing a ˜34-43 kbp double-stranded DNA genome within the core (3). Fifty-one human adenovirus (AdHu) serotypes have so far been described, based on serological studies of cross-neutralising antibody responses to the hexon protein and terminal knob of the penton fibre. These serotypes have been further grouped into six subgroups or species (A-F) within the Mastadenovirus genus, based on phylogenetic analysis and their haemagglutination reaction (1). Adenoviruses show a broad tropism with most human serotypes, including the widely studied AdHu5 (subgroup C), initially binding to the Coxsackie adenovirus receptor (CAR) (4), followed by internalisation of the virion upon the interaction of Arg-Gly-Asp (RGD) motifs in the penton base with α_(v)β₃- or α_(v)β₅-integrins (5). CAR is widely expressed on many cell types, but only on dendritic cells (DCs) at low levels. Some viruses within subgroup B do not bind CAR. AdHu35, for example, binds the complement regulatory protein membrane cofactor protein (MCP/CD46) (6), whilst AdHu3 attaches to the costimulatory molecules CD80 (B7.1) and CD86 (B7.2) expressed by APCs (7). Some serotypes are ubiquitous and infect most children during early infancy, such as AdHu1, 2 and 5, causing acute mild upper respiratory infections. Others, however, can lead to serious and even fatal infections, such as pneumonia (AdHu3 and 7), especially in immunocompromised individuals (8) and children (9).

Adenoviruses were initially developed as vehicles for gene therapy. Attempts to replace missing or faulty genes by adenoviral gene transfer were largely unsuccessful in experimental animals and human volunteers alike due to innate and adaptive immune responses induced by the adenoviral antigens (3). However, the demonstration by gene therapists of the induction of potent cellular and humoral transgene-specific immune responses pioneered the use of these viruses as vaccine vectors with highly successful results first demonstrated using a recombinant rabies virus glycoprotein (10). The adenoviral genome is well characterised and comparatively easy to manipulate (11, 12). Deletion of crucial regions of the viral genome, such as E1, renders the vectors replication-defective, which increases their predictability and eliminates unwanted pathogenic side effects. Replication-deficient adenoviruses can be grown to high titre in tissue culture, using cell lines that provide the missing essential E1 gene products in trans (13). They can be applied systemically as well as through mucosal surfaces and their relative thermostability facilitates their clinical use. Whilst bovine, porcine, and ovine adenoviruses are being explored for veterinary use (3), studies of adenovirus vectors of differing human serotype have shown variable immunogenicity. The majority of studies now focus on the most promising candidates, including AdHu5, AdHu35 and AdHu11. These vectors can induce potent and protective T and B cell-mediated responses against a range of viral and parasitic encoded antigens (10, 14-17). However, problems surrounding pre-existing immunity to ubiquitous viruses such as AdHu5 and AdHu35 remain a big hurdle to the clinical deployment of these vectors. Depending on the region under study, 35-80% of human adults carry AdHu5-neutralising antibodies, and 5-15% AdHu35-neutralising antibodies (18).

E1-deleted replication-defective adenovirus vectors can be generated from “molecular clones”, in which the entire genome is carried within a bacterial plasmid (11). Vaccine constructs can be ligated into the E1-deletion site using commercially available kits. Upon removal of the bacterial sequences by restriction enzyme digest, and exposure of the inverted terminal repeats (ITRs), the plasmid can be transfected into a packaging cell line that supplies the essential E1 gene product in trans, thus generating the pure recombinant virus.

The adenoviral capsid will only allow a 5% increase in genome size before efficient packaging and viral stability is disrupted—an extra 1.8 kbp in the case of the well-studied vector AdHu5 (3). Vectors deleted of E1 and the non-essential E3 region (21) can accommodate up to 7.5 kbp of foreign DNA and remain the leading choice for vaccine studies using this vector.

Therefore, according to a first aspect of the present invention there is provided an immunogenic composition comprising an adenoviral vector, said adenoviral vector further comprising a promoter comprising a fragment of the 5′ untranslated region of the CMV IE1 gene including intron A and a nucleic acid sequence encoding a pathogen or tumour antigen under the control of said promoter; wherein said antigen is not a murine malaria parasite antigen.

In one embodiment, the composition may be a vaccine composition. Preferably, the vaccine composition is suitable for human administration and can be used to elicit a protective immune response against the encoded antigen.

In a preferred embodiment, the adenoviral vector is a simian adenoviral vector. More preferably, the simian adenoviral

In a preferred embodiment, the adenoviral vector is a simian adenoviral vector. More preferably, the simian adenoviral vector is AdC6 (C6), AdC7 (C7), AdC9 (C9) vector. These viruses are detailed by S. Roy et al. Virology (2004) Volume 324, pp 361-372. Therein AdC6 is referred to as SAdV-23; AdC7 is referred to as SAdV-24; and AdC9 is referred to as SAdV-25. In other publications AdC9 is also called AdC68 (e.g. Fitzgerald et al. J Immunology 2003, 170:1416-22).

It will be understood that the development of simian adenovirus vectors, for example, chimpanzee adenoviruses, against which pre-existing immunity is prevalent neither in humans (1-2%) nor in some other simian species, such as rhesus macaques, often used for pre-clinical testing (19, 20) is desirable.

It will be further understood that in many applications it is preferable for the adenovirus vector to be replication deficient meaning that they have been rendered incapable of replication because of a functional deletion, or complete removal, of a gene encoding a gene product essential for viral replication. By way of example, the vectors of the invention may be rendered replication defective by removal of all or a part of the E1 gene, and optionally also the E3 region and/or the E4 region.

It should be understood that CMV promoters are well known in the art. Numerous versions of the CMV Immediate Early (IE) promoter exist as shown in FIG. 1. It is known that these can be used to drive antigen expression in host eukaryotic cells (22). The CMV IE enhancer-promoter has been shown to cause high levels of transgene expression in eukaryotic tissues when compared with other promoters. A DNA vaccine expressing the HIV-1 antigens Gag/Env under the control of the CMV promoter, rather than the endogenous AKV murine leukaemia virus long terminal repeat, was shown to be more immunogenic in macaques (23).

It is further known that inclusion of the CMV intron A results in enhanced transgene expression over the CMV IE enhancer-promoter alone in vitro and in vivo (24, 25) using plasmid DNA vectors.

However, no assessments of the comparative immunogenicity of these vectors with different promoters has been undertaken.

More recently expression of a firefly luciferase gene has been assessed using an AdHu5 vector and better expression observed with the addition of the intron A sequence (26). Again no studies of immune responses were undertaken. It has been suggested that inclusion of the intron may enhance the rate of polyadenylation and/or nuclear transport associated with splicing of pre-mRNA primary transcripts (27). Such research on promoter function with adenovirus and plasmid vectors has been directed at enhancing transgene expression in order to improve the efficacy of gene therapy vectors, where the desired outcome is high level prolonged expression of the transgene.

It will be apparent to the skilled person that, although some expression is required for immunogenicity, increased expression of a gene does not correlate with increased immunogenicity. Indeed increased expression of a transgene may lead to vector instability or non-viability of the recombinant virus.

It will be apparent that the antigen can be any antigen of interest either exogenous or endogenous. Exogenous antigens include all molecules found in infectious organisms. For example bacterial immunogens, parasitic immunogens and viral immunogens.

Bacterial sources of these immunogens include those responsible for bacterial pneumonia, meningitis, cholera, diphtheria, pertussis, tetanus, tuberculosis and leprosy.

Parasitic sources include malarial parasites, such as Plasmodium, as well as trypanosomal and leishmania species.

Viral sources include poxviruses, e.g., smallpox virus, cowpox virus and orf virus; herpes viruses, e.g., herpes simplex virus type 1 and 2, B-virus, varicella zoster virus, cytomegalovirus, and Epstein-Barr virus; adenoviruses, e.g., mastadenovirus; papovaviruses, e.g., papillomaviruses such as HPV16, and polyomaviruses such as BK and JC virus; parvoviruses, e.g., adeno-associated virus; reoviruses, e.g., reoviruses 1, 2 and 3; orbiviruses, e.g., Colorado tick fever; rotaviruses, e.g., human rotaviruses; alphaviruses, e.g., Eastern encephalitis virus and Venezuelan encephalitis virus; rubiviruses, e.g., rubella; flaviviruses, e.g., yellow fever virus, Dengue fever viruses, Japanese encephalitis virus, Tick-borne encephalitis virus and hepatitis C virus; coronaviruses, e.g., human coronaviruses; paramyxoviruses, e.g., parainfluenza 1, 2, 3 and 4 and mumps; morbilliviruses, e.g., measles virus; pneumovirus, e.g., respiratory syncytial virus; vesiculoviruses, e.g., vesicular stomatitis virus; lyssaviruses, e.g., rabies virus; orthomyxoviruses, e.g., influenza A and B; bunyaviruses e.g., LaCrosse virus; phieboviruses, e.g., Rift Valley fever virus; nairoviruses, e.g., Congo hemorrhagic fever virus; hepadnaviridae, e.g., hepatitis B; arenaviruses, e.g., 1 cm virus, Lasso virus and Junin virus; retroviruses, e.g., HTLV I, HTLV II, HIV-1 and HIV-2; enteroviruses, e.g., polio virus 1, 2 and 3, coxsackie viruses, echoviruses, human enteroviruses, hepatitis A virus, hepatitis E virus, and Norwalk-virus; rhinoviruses e.g., human rhinovirus; and filoviridae, e.g., Marburg (disease) virus and Ebola virus.

Antigens from these bacterial, viral and parasitic sources can be considered as exogenous antigens because they are not normally present in the host and are not encoded in the host genome.

In contrast, endogenous antigens are normally present in the host or are encoded in the host genome, or both. The ability to generate an immune response to an endogenous antigen is useful in treating tumours that bear that antigen, or in neutralising growth factors for the tumour. An example of the first type of endogenous antigen is HER2, the target for the monoclonal antibody called Herceptin. An example of the second, growth factor, type of endogenous antigen is gonadotrophin releasing hormone (called GnRH) which has a trophic effect on some carcinomas of the prostate gland.

Preferably, the antigen is an antigen from an infectious pathogen of humans or livestock.

In one preferred embodiment, the antigen is from a pathogen which causes malaria. Preferably, the antigen is a P. falciparum antigen.

Preferably, the malaria antigen is a pre-erythrocytic or blood-stage malaria antigen.

In particularly preferred embodiments of the present invention, the malaria antigen is ME-TRAP, CSP, MSP-1 or fragments thereof, or AMA1.

Preferably, when the malaria antigen is an MSP-1 antigen it has the sequence of PfM117 (SEQ ID NO. 1) or PfM128 (SEQ ID NO. 3).

Malaria is a disease against which it has been very difficult to generate protective immunity in both humans and small animal models. Thus the results discussed below indicate that the use of the immunisation approaches described herein have general potential for use in generating very potent vaccines in humans and other species.

In a further preferred embodiment, the antigen in a mycobacterial antigen. Preferably, the antigen is a M. tuberculosis antigen. More preferably, the antigen is M. tuberculosis antigen 85A.

The inventors have found that the enhanced antigen expression resulting from the presence of the long CMV promoter including intron A leads to a remarkably large and surprising increase in the immunogenic potency of these vaccine vectors, and to enhanced protective efficacy against pathogen challenge.

The above immunogenic viral vector compositions, may be formulated into pharmaceutical dosage forms, together with suitable pharmaceutically acceptable carriers, such as diluents, fillers, salts, buffers, stabilizers, solubilizers, etc. The dosage form may contain other pharmaceutically acceptable excipients for modifying conditions such as pH, osmolarity, taste, viscosity, sterility, lipophilicity, solubility etc.

Suitable dosage forms include solid dosage forms, for example, tablets, capsules, powders, dispersible granules, cachets and suppositories, including sustained release and delayed release formulations. Powders and tablets will generally comprise from about 5% to about 70% active ingredient. Suitable solid carriers and excipients are generally known in the art and include, e.g. magnesium carbonate, magnesium stearate, talc, sugar, lactose, etc. Tablets, powders, cachets and capsules are all suitable dosage forms for oral administration.

Liquid dosage forms include solutions, suspensions and emulsions. Liquid form preparations may be administered by intravenous, intracerebral, intraperitoneal, intradermal, parenteral or intramuscular injection or infusion. Sterile injectable formulations may comprise a sterile solution or suspension of the active agent in a non-toxic, pharmaceutically acceptable diluent or solvent. Suitable diluents and solvents include sterile water, Ringer's solution and isotonic sodium chloride solution, etc. Liquid dosage forms also include solutions or sprays for intranasal administration.

Aerosol preparations suitable for inhalation may include solutions and solids in powder form, which may be combined with a pharmaceutically acceptable carrier, such as an inert compressed gas.

Also encompassed are dosage forms for transdermal administration, including creams, lotions, aerosols and/or emulsions. These dosage forms may be included in transdermal patches of the matrix or reservoir type, which are generally known in the art.

Pharmaceutical preparations may be conveniently prepared in unit dosage form, according to standard procedures of pharmaceutical formulation. The quantity of active compound per unit dose may be varied according to the nature of the active compound and the intended dosage regime.

The active agents are to be administered to human subjects in “therapeutically effective amounts”, which is taken to mean a dosage sufficient to provide a medically desirable result in the patient. The exact dosage and frequency of administration of a therapeutically effective amount of active agent will vary, depending on such factors as the nature of the active substance, the dosage form and route of administration.

The medicaments and pharmaceutical compositions of the present invention may be administered systemically or locally. This is applicable to both the use and method aspects of the invention equally. Systemic administration may be by any form of systemic administration known, for example, orally, intravenously or intraperitoneally. Local administration may be by any form of local administration known, for example topically.

In particularly preferred embodiments the pharmaceutical composition includes at least one pharmaceutically acceptable excipient.

According to a second aspect of the present invention there is provided an adenoviral vector comprising a promoter further comprising a fragment of the 5′ untranslated region of the CMV IE1 gene including intron A and a nucleic acid sequence encoding a pathogen or tumour antigen under the control of said promoter for use as a medicament.

Preferably, the adenoviral vector is a simian adenoviral vector.

Preferably the adenoviral vector is replication deficient.

Preferably, the antigen is an antigen from an infectious pathogen of humans or livestock.

According to a third aspect of the present invention there is provided the use of an adenoviral vector comprising a promoter further comprising a fragment of the 5′ untranslated region of the CMV IE1 gene including intron A and a nucleic acid encoding a malarial antigen in the manufacture of a vaccine or immunotherapeutic for the prevention or treatment of malaria.

Preferably, the malaria antigen is not from a murine parasite.

Preferably, the adenoviral vector is a simian adenoviral vector.

Preferably the adenoviral vector is replication deficient.

In a preferred embodiment, the encoded malaria antigen is a P. falciparum antigen. More preferably, the malarial antigen is a pre-erythrocytic or blood-stage malaria antigen. Even more preferably, the malarial antigen is ME-TRAP, CSP, MSP-1 or fragments thereof, or AMA1.

In a most preferred embodiment, when the malarial antigen is an MSP-1 antigen it has the sequence of PfM117 (SEQ ID NO. 1) or PfM128 (SEQ ID NO. 3).

According to a fourth aspect of the present invention there is provided the use of an adenoviral vector comprising a promoter further comprising a fragment of the 5′ untranslated region of the CMV IE1 gene including intron A and a nucleic acid encoding a M. tuberculosis antigen in the manufacture of a vaccine or immunotherapeutic for the prevention or treatment of tuberculosis.

Preferably, the adenoviral vector is a simian adenoviral vector.

Preferably the adenoviral vector is replication deficient.

In a preferred embodiment, the encoded antigen is the M. tuberculosis antigen 85A.

According to a fifth aspect of the present invention there is provided an adenoviral vector comprising a promoter further comprising a fragment of the 5′ untranslated region of the CMV IE1 gene including intron A and a nucleic acid encoding a malarial antigen for use in the prevention or treatment of malaria.

Preferably, the malaria antigen is not from a murine parasite.

Preferably, the adenoviral vector is a simian adenoviral vector.

Preferably the adenoviral vector is replication deficient.

Preferably, the malaria antigen is a P. falciparum antigen.

Preferably, the malaria antigen is a pre-erythrocytic or blood-stage malaria antigen.

Preferably, the malaria antigen is ME-TRAP, CSP, MSP-1 or fragments thereof, or AMA1. More preferably, the malaria antigen is an MSP-1 antigen has the sequence of PfM117 (SEQ ID NO. 1) or PfM128 (SEQ ID NO. 3).

According to a sixth aspect of the present invention, there is provided an adenoviral vector comprising a promoter further comprising a fragment of the 5′ untranslated region of the CMV IE1 gene including intron A and a nucleic acid encoding a M. tuberculosis antigen for use in the prevention or treatment of tuberculosis.

Preferably, the adenoviral vector is a simian adenoviral vector.

Preferably, the adenoviral vector is replication deficient.

In a preferred embodiment, the encoded antigen is M. tuberculosis antigen 85A.

It will be readily apparent that the medicaments described in any of the above aspects may comprise one or more pharmaceutically acceptable vehicles, carriers, diluents, excipients or adjuvants.

According to a seventh aspect of the present invention there is provided a product, combination or kit comprising;

a) a priming composition comprising an adenoviral vector, said adenoviral vector further comprising a long heterologous promoter, wherein the promoter is a fragment of the 5′ untranslated region of the CMV IE1 gene including intron A, and at least one nucleic acid sequence encoding a pathogen or tumour antigen, wherein the antigen is not a murine malaria parasite antigen; and

b) a boosting composition comprising a recombinant pox virus vector, said pox virus vector further comprising at least one nucleic acid sequence encoding a pathogen or tumour antigen which is the same as at least one antigen of the priming composition.

Preferably, the adenoviral vector is a simian adenoviral vector. More preferably, the simian adenoviral vector is AdC6 (C6), AdC7 (C7), or AdC9 (C9) vector.

Preferably, the antigen is not a murine malaria parasite antigen.

In a preferred embodiment, the promoter excludes Exon B.

Preferably, the antigen is an antigen from an infectious pathogen of humans or livestock.

In one preferred embodiment, the antigen is from a pathogen which causes malaria. Preferably, the antigen is a P. falciparum antigen. More preferably, a pre-erythrocytic or blood-stage malarial antigen. Even more preferably, the malarial antigen is ME-TRAP, CSP, MSP-1 or fragments thereof, or AMA1.

When the malarial antigen is an MSP-1 antigen preferably it has the sequence of PfM117 (SEQ ID NO. 1) or PfM128 (SEQ ID NO. 3).

In a further preferred embodiment, the antigen in a mycobacterial antigen. More preferably, the antigen is a M. tuberculosis antigen. Even more preferably, the antigen is M. tuberculosis antigen 85A.

Also provided is the use of the combination for production of a kit for generating a protective T cell response against at least one target antigen of a pathogen or tumour in a subject.

According to an eighth aspect of the present invention there is provided a method of eliciting an immune response in a subject comprising administering an effective amount of an immunogenic composition or vaccine according to the first aspect of the present invention sufficient to elicit an immune response.

It will be apparent that the subject can be administered the composition or vaccine for either prophylactic or immunotherapeutic purposes, depending on the antigen.

In a preferred embodiment, the subject is immunised using a heterologous prime-boost regimen.

The skilled person will understand that heterologous prime-boost refers to a regimen wherein an effective amount of a first immunogenic composition or vaccine according to the present invention is administered to an individual at a first time point and subsequently an effective amount of a second immunogenic composition or vaccine encoding the same antigen as the immunogenic composition or vaccine according to the present invention is administered at a second time point. It will be understood that in an heterologous prime-boost regimen the first and second immunogenic composition or vaccines are different.

Preferably, the second immunogenic composition or vaccine is administered 2-8 weeks after the first immunogenic composition or vaccine.

It will be readily apparent to the skilled person that the term subject as used in the present invention relates to any animal subject. This may particularly be a mammalian subject, including a human.

Thus products of the invention may be useful not only in human use but also in veterinary uses, for example in the treatment of domesticated mammals including livestock (e.g. cattle, sheep, pigs, goats, horses or in the treatment of wild mammals, such as those captive in zoos).

In another aspect, the product of the invention may be used for the treatment of non-mammalian subjects, including fowl such as chickens, turkeys, duck, geese and the like.

According to a ninth aspect of the present invention there is provided a simian adenoviral vector comprising a long heterologous promoter, wherein the promoter is a fragment of the 5′ untranslated region of the CMV IE1 gene including intron A and at least one nucleic acid sequence encoding a pathogen or tumour antigen of interest.

Preferably, the promoter does not include exon B.

Preferably the simian adenoviral vector is replication deficient.

Preferably, the antigen is an antigen from an infectious pathogen of humans or livestock.

In one preferred embodiment, the antigen is from a pathogen which causes malaria. Preferably, the antigen is a P. falciparum antigen. More preferably, a blood-stage malarial antigen. Even more preferably, the malarial antigen is ME-TRAP, CSP, MSP-1 or fragments thereof, or AMA1.

When the malarial antigen is an MSP-1 antigen preferably it has the sequence of PfM117 (SEQ ID NO. 1) or PfM128 (SEQ ID NO. 3).

In a further preferred embodiment, the antigen in a mycobacterial antigen. More preferably, the antigen is a M. tuberculosis antigen. Even more preferably, the antigen is M. tuberculosis antigen 85A.

According to a tenth aspect of the present invention there is provided a method for enhancing the T cell immunogenicity of an immunogenic adenoviral vector composition or vaccine according to the first aspect, comprising administering said vaccine in combination with a CpG adjuvant.

It will be apparent that the CpG adjuvant can be administered prior to, concomitantly with, or subsequently to said immunogenic composition or vaccine.

According to an eleventh aspect of the present invention there is provided a composition comprising an immunogenic adenoviral vector composition or vaccine according to first aspect and a CpG adjuvant.

According to a twelfth aspect of the present invention there is provided the composition according to the eleventh aspect for use as a medicament.

According to a thirteenth aspect there is provided a kit comprising the immunogenic adenoviral vector composition or vaccine of first aspect and a CpG adjuvant for use in generating an immune response in a subject against at least one pathogen or tumour antigen.

It will be understood that an immunogenic composition referred to in any of the above aspects may in certain embodiments be a vaccine.

It will be apparent that the antigen according to any aspect of the present invention may be any antigen of interest as described in relation to the first aspect.

It will be apparent that any feature described as preferred in connection with one aspect of the invention is also preferred in relation to other aspects of the invention unless otherwise stated, and that preferred embodiments relating to one feature are disclosed in combination with preferred embodiments relating to other features.

The invention will now be further described with reference to the following examples and figure in which:

FIG. 1 shows CMV Promoters.

1) Complete CMV IE promoter sequence from GenBank. 2) The “long” 1.9 kbp version of the promoter referred in this document. 3) Promoter with chimeric intron from Promega® (Southampton, UK) used to express ME-TRAP. 4) The “small” 0.6 kbp version of the promoter referred to in this document.

FIG. 2 shows quantification of antigen expression by quantitative real-time RT-PCR.

293A cells were infected with AdHu5 expressing (a) MSP-1₄₂ or (b) 85A, under the control of the long or small promoter. Cells were harvested into RLT buffer, and the RNA extracted and reverse transcribed into cDNA. The levels of MSP-1₄₂, 85A and AdHu5 E4orf1 cDNA target sequences were measured by real-time PCR. Relative gene expression was calculated as the ratio of target antigen mRNA copies to E4orf1 copies. Each column represents the mean ratio±S.E.

FIG. 3 shows quantification of MSP-1₄₂ antigen expression by Western Blot.

293A cells were infected with no virus (lane 1) Ad42SP (lane 2) or Ad42LP (lane 3) in cell culture medium excluding FCS. Cell culture supernatants were harvested once 100% CPE was evident, and concentrated by centrifugation through Centricon YM 30 tubes (Millipore, Watford, UK). Proteins from cell culture supernatants were separated by SDS-PAGE and electroblotted onto nitrocellulose membrane, before staining with HRP-conjugated mAb to the C-terminal PK/V5 tag. The blot was developed and exposed to photographic film.

The predicted molecular mass for MSP-1₄₂-PK is 46 kDa.

FIG. 4. shows peptide-specific IFN-γ-secreting T cell responses induced by (a) Ad-MSP-1₄₂ or (b) Ad-85A vaccination.

BALB/c mice were immunised i.d. with 10¹⁰ vp of each adenovirus, and responses measured in the spleens of immunised mice 14 days post-immunisation by ex-vivo IFN-γ ELISPOT. Columns represent the mean number of IFN-γ SFC per million splenocytes±S.E. (n=3 mice/group). * p≦0.05, ** p≦0.01, comparing responses between groups that were immunised with AdHu5 vectors expressing the relevant antigen under the control of the long (LP) or short (SP) promoter.

FIG. 5. shows MSP-1₁₉-specific whole IgG antibody responses induced by Ad42SP or Ad42LP.

BALB/c mice were immunised i.d. with 10¹¹ vp Ad42SP or with 5×10¹⁰ vp Ad42LP. Whole IgG responses against MSP-1₁₉ were measured by anti-GST-MSP-1₁₉ ELISA in the serum of mice 13 days post-immunisation. GST controls all negative (data not shown). Columns represent the mean log 10 endpoint titre±95% C.I. (n=3 mice/group). * p≦0.05, comparing responses between groups.

FIG. 6. shows kinetics of MSP-1₁₉-specific whole IgG antibody responses induced by Ad42LP.

BALB/c mice were immunised once i.d. with 5×10¹⁰ vp Ad42 at week 0. Whole IgG responses against MSP-1₁₉ were assayed by anti-GST-MSP-1₁₉ ELISA in the serum of mice taken at 14 day intervals. Points represent the results of two experiments as the mean log 10 endpoint titre±95% C.I. (n=18 mice). *** p≦0.001, comparing differences between time points by paired analysis of data from individual mice.

FIG. 7. shows MSP-1₁₉-specific IgG antibody responses induced by AdM42 prime-boost vaccination.

BALB/c mice were immunised i.d. with 5×10¹⁰ vp Ad42LP and boosted i.d. with 5×10⁷ pfu MVA expressing the same antigen either two or eight weeks later. Whole IgG responses against MSP-1₁₉ were measured by anti-GST-MSP-1₁₉ ELISA in the serum of mice 13 days after the second immunisation. Columns represent the results of two or three experiments as the mean log 10 endpoint titre±95% C.I. (n=11-22 mice/group). *** p≦0.001, comparing responses between the two groups.

FIG. 8. shows P. yoelii sporozoite challenge of AdM42 (8 wks) immunised BALB/c mice.

BALB/c mice were immunised as described in table 1, and challenged with 50 P. yoelii sporozoites 14 days after the final immunisation (day 0). Blood-stage parasitaemia was monitored daily by Giemsa-stained thin-blood smear from day 5, and percentage pRBCs calculated. Results are shown for: (a) unimmunised naïve controls n=6; (b) AdM42 (8 wks) n=6.

Unprotected mice which succumbed to infection or were sacrificed (at 80% blood-stage parasitaemia) are indicated by the cross symbol t.

FIG. 9 shows immunogenicity to ME.TRAP.

(a) Breadth of the immune response to ME.TRAP. BALB/c mice were immunized with 1×10⁹ vp of adenoviral vectors coding for ME.TRAP. Immune responses were measured 2 weeks later by ELISPOT after stimulation of cells with overlapping peptides covering the whole sequence of the ME.TRAP transgene. Data are mean±s.d. for three mice per group. (b) Kinetics of the immune response to ME.TRAP. BALB/c mice were immunized with adenoviral (1×10¹⁰ vp) and poxviral vectors (1×10⁷ pfu). The magnitude of the immune response was measured after stimulation of splenocytes with Pb9 peptide and detection of IFNgamma⁺-producing CD8⁺ T cells by flow cytometry at different intervals. (c) Total number of IFNgamma⁺ CD8⁺ T cells per spleen during the peak of the effector and memory responses for each vector. Calculations were performed in the same groups of mice from FIG. 1 b. (d) The percent of IFNgamma⁺ CD8⁺ T cells from representative mice upon Pb9 peptide stimulation. Upper panel shows the peak of the effector response for each vector (20 days post-prime for adenoviral vectors and 7 days post-prime for poxviral vectors) The memory phase was measured at day 60 post-prime. Data are mean±s.e.m. for three mice per group.

FIG. 10 shows immunogenicity to ME.TRAP in C57BL/6 mice.

(a) Breadth of the immune response. Mice were immunized with 1×10⁹ vp of adenoviral vectors coding for ME.TRAP. Immune responses were measured 2 weeks later by ELISPOT after stimulation of cells with overlapping peptides covering the whole sequence of the ME.TRAP transgene. Data are mean±s.d. for three mice per group. (b) The percent of IFNgamma⁺ CD8⁺ and CD4⁺ T cells from a pool of 3 mice upon peptide stimulation. Upper panel shows the CD8⁺ T-cell response for each vector (20 days post-prime) and lower panel shows the CD4+ T-cell response.

FIG. 11. shows acquisition of effector phenotype and cytolytic functions by CD8⁺ T cells at different intervals post-vaccination.

BALB/c mice were immunized as described in FIG. 1. Data show percentage of CD8⁺ IFNgamma⁺ CD43^(hi) (a) and CD8⁺ IFNgamma⁺ Granzyme B coexpression (b). (c) Granzyme B expression from representative mice at indicated days post-prime. Histogram shows GrB expression (white background) after staining with anti-human GrB, compared to an isotype control (gray background). The number corresponds to MFI of the positive sample (black solid line). Data in graphs are mean±s.e.m. for three mice per group.

FIG. 12. shows analysis of the memory response by phenotypic markers.

BALB/c mice were immunized as described in FIG. 1. Splenocytes were co-stained for CD8, IFNgamma⁺ and (a) CD62L, (b) CD127, (c) IL-2 and (d) CD27. Bars show percentages of cells within the IFNgamma⁺ compartment. Data are mean±s.e.m. for three mice per group.

FIG. 13. shows analysis of the antibody responses to Pf TRAP.

IgG antibodies against the TRAP region were analyzed by ELISA in serum from groups of at least 3 BALB/c mice after 2 weeks of immunization with individual vectors. Results were reported as a dilution factor needed for a sample in order to reach the O.D. of a naïve serum.

FIG. 14. shows immunogenicity of various adenoviruses encoding the PfM115 insert in BALB/c mice.

After a single immunisation intradermally (5×10¹⁰ vp) with the various adenoviral vectors at week 0 good antibody levels were detected to the 19 Kd fragment of PfMSP1 at 2 weeks in all mice and these titres increased up to week 8 when all mice were administered an MVA encoding the same insert, leading to an further increase in antibody titres. The simian adenoviral vectors appears similar in immunogenicty to the AdHu5 vector. The AdHu5PfM115C4bp encodes an additional C-terminal core sequence from the complement protein C4bp.

FIG. 15 shows assessment of the potential immune enhancing effect of a CpG sequence (CpG 1826) added to the AdHu5 PfM115 adenovirus vector.

BALB/c mice were immunised intradermally on one occasion and T cell responses evaluated 14 days later. A large pool of overlapping peptides spanning the insert were used to evaluate CD8 (above) and CD4 (below) T cell IFN-gamma responses.

EXAMPLES

In the following Examples a number of antigens have been used in the adenovirus vector vaccines of the current invention:

The Mycobacterium tuberculosis antigen 85A (28, 29).

The 42 kDa C-terminus of the blood-stage malarial antigen merozoite surface protein-1 (MSP-1₄₂) from the murine parasite Plasmodium yoelii (30).

The malaria sporozoite antigen circumsporozoite protein (CSP) from the murine malaria parasite P. berghei

The pre-erythrocytic malarial antigen insert multi-epitope string—thrombospondin-related adhesion protein (ME-TRAP) from P. falciparum (31, 32).

A fusion protein of regions of the P. falciparum blood-stage antigen MSP-1 denoted PfM117

A fusion protein of regions of the P. falciparum blood-stage antigen MSP-1 denoted PfM128

Example 1 Production of Adenovirus Vector Vaccines Containing Murine Malaria Antigens and a Tuberculosis Antigen

1.1 Enhancement of Antigen Expression by CMV Promoter in Recombinant AdHu5 Vectors.

AdHu5 vectors encoding murine malaria P. yoelii MSP-1₄₂ or antigen85A from M. tuberculosis were compared, using vectors which drive transgene expression by either the “small” 0.6 kbp version of the CMV IE promoter (lacking intron A), or the “long” 1.9 kbp version of the promoter (with regulatory element, enhancer and intron A). The small and long versions of the promoter are referred to as SP and LP respectively. The level of antigen expression by AdHu5 vectors was assayed in vitro by quantitative real-time RT-PCR (FIG. 2). The level of antigen expression was normalised to the AdHu5 E4orf1 transcript. In both cases, significantly higher levels of antigen expression were measured following infection of 293A cells with AdHu5 vectors expressing antigen under the control of the long promoter. The overall level of antigen expression may be antigen dependent, given both vectors encoding 85A expressed significantly higher levels of antigen compared to either vector encoding MSP-1₄₂. These results were confirmed for the vectors encoding MSP-1₄₂ by Western Blot (FIG. 3). The MSP-1₄₂ antigen includes the PK epitope (amino acid sequence IPNPLLGLD; SEQ ID NO: 8) as a C-terminal fusion. Antigen is detected using the monoclonal antibody anti-PK (also known as anti-V5) from Serotec (Oxford, UK).

1.2 Enhancement of T Cell Immunogenicity by CMV Promoters in Recombinant AdHu5 Vectors.

Groups of BALB/c mice were immunised intradermally (i.d.) with 10¹⁰ vp of each adenovirus, and responses measured in the spleen to known CD8⁺ and CD4⁺ T cell epitopes 14 days later by ex-vivo interferon-gamma (IFN-γ) ELISPOT (FIG. 4). The epitopes in MSP-1₄₂ are all known H-2^(d) class I-restricted epitopes (FIG. 4 a). pll is a known H-2^(d) class I-restricted epitope in 85A, whilst p15 is class II-restricted (FIG. 4 b). Responses were only detected against known epitopes in MSP-1₄₂ when mice were immunised with Ad42LP, whereas responses to 85A were induced by both vectors, with those against p15 tending to be stronger in the Ad85ALP group. These data correlate with the level of antigen expression measured by real-time RT-PCR (FIG. 2).

1.3 Enhancement of Antibody Immunogenicity by CMV Promoters in Recombinant AdHu5 Vectors.

Groups of BALB/c mice were immunised i.d. with 10¹⁰ vp of Ad42LP or Ad42SP. Whole IgG antibody responses against the C-terminus of MSP-1₄₂ (MSP-1₁₉) were assayed by ELISA two weeks later (FIG. 5). There was no detectable antibody responses against MSP-1₁₉ following Ad42SP immunisation, whereas Ad42LP primed a significantly higher response, with an endpoint titre of approximately 1000. This response, induced by Ad42LP, continues to increase over time, reaching a plateau by 6-8 weeks (FIG. 6). This antibody response can be boosted to a significantly higher level by MVA encoding the same antigen. Antibody responses are significantly higher following this heterologous AdM prime-boost regime, if Ad42LP primed mice are boosted 8 weeks rather than 2 weeks later (FIG. 7).

1.4 Protection of Mice Against Lethal Blood-Stage P. Yoelii Challenge by AdM-MSP-1₄₂ Immunisation.

The protection provided by the prime boost regime was investigated by examination of the protection provided by AdM-MSP-1₄₂ immunisation against lethal blood-stage P. yoelii challenge in mice. Groups of BALB/c mice were immunised i.d. with 5×10¹⁰ vp of Ad42LP and boosted with MVA expressing the same antigen two or eight weeks later. All immunisation regimes utilised the Ad42LP vector, and MVA expressing the same antigen. Mice were challenged i.v. with 10⁴ P. yoelii pRBCs 14 days after the final immunisation. Homologous prime-boost regimes were included as a comparison. 76% of mice immunised with the AdM42 regime using an eight week prime-boost interval were completely protected against a lethal challenge with 10⁴ parasitised red blood cells (pRBCs) as shown in Table 1.

TABLE 1 No. Mice Median (Range) Peak % Immunisation Protected/ % Parasitaemia of Regime Challenged Protected Protected Mice AdM42 (2 wks) 0/6 0% N/A AdM42 (8 wks) 4/5 + 4/6 + 76%  1.2% (0.004%-27.7%) 5/6 MM42 (8 wks) 0/3 0% N/A AdAd42 (8 wks) 0/3 0% N/A Naïve 0/4 + 0/4 + 0% N/A 0/4

The table outlines the results from individual experiments and the overall level of protective efficacy. The median and range of peak parasitaemia of those mice that survived in each group are included. Exponential parasite growth results in ≧80% blood-stage parasitaemia within 5-7 days post-infection in naïve or unprotected mice, at which point mice are sacrificed. Protected mice can control and ultimately clear blood-stage malaria infection.

These results could be replicated in a second strain of mouse, and in this case 100% of C57BL/6 mice survived challenge, compared to none of the naïve unimmunised controls as shown in Table 2.

TABLE 2 No. Mice Median (Range) Peak Immunisation Protected/ % % Parasitaemia of Regime Challenged Protected Protected Mice AdM42 (8 wks) 6/6 100% 14.7% (3.7%-56.4%) Naïve 0/6  0% N/A

100% of BALB/c mice immunised with this regime were also protected against a challenge with 50 P. yoelii sporozoites—the natural mode of malaria infection (FIG. 8).

1.5 Sterile Protection of Mice to P. berghei Sporozoite Challenge by AdHu5-PbCSP Immunisation.

AdHu5 vector recombinant for the circumsporozoite protein (CSP) from P. berghei was generated, with the antigen under the control of the long promoter (33). BALB/c mice were immunised as indicated in Table 3. Some groups of mice received a single immunisation i.d. of AdHu5 expressing PbCSP and were challenged two or eight weeks later. The remaining groups were immunised with heterologous prime-boost regimes using AdHu5 and MVA expressing PbCSP. The time interval in weeks between the two immunisations is indicated in parentheses. All immunisation regimes utilised the AdHu5 vector expressing PbCSP under the control of the long promoter. Mice were challenged i.v. with 10³ P. berghei sporozoites. Blood-stage parasitaemia was monitored daily by Giemsa-stained thin-blood smear from day 5 in challenged mice. Mice are protected given the continued absence of patent blood-stage parasitaemia up until day 21. 33% of mice were protected against challenge following a single immunisation with Ad-PbCSP and infection two weeks later as shown in Table 3.

TABLE 3 Time Interval between No. Mice Immunisation Immunisation and Protected/ % Regime Challenge Challenged Protection Ad-PbCSP 2 weeks  4/12 33% Ad-PbCSP 8 weeks 1/6 18% Naïve 2 weeks/8 weeks  0/12  0% Ad-MVA 2 weeks 66% PbCSP (2 week prime- boost interval) Ad-MVA 2 weeks 100%  PbCSP (8 week prime boost interval) Naïve 2 weeks  0%

Immunisation with Ad-PbCSP induces a potent CDS⁺ T cell response against the H-2^(d) class I-restricted epitope, Pb9 (34). If these mice are boosted with MVA encoding PbCSP eight weeks later, then 100% of mice are refractory to P. berghei sporozoite challenge Table 3 and Ref. (33).

Example 2 Production of Pre-Erythrocytic Human Malaria (P. falciparum) Antigen Vaccines with Human and Simian Adenovirus Vectors

Vaccination with pre-erythrocytic vaccines have shown particular promise for tacking the huge global health problem of malaria (1,2) with some efficacy in clinical trials from immunity to this stage of the malaria life cycle directed towards the sporozoite and subsequent intrahepatic schizont (37). The cellular immune response has previously been shown to be important in pre-erythrocytic immunity with CD8⁺ T cells and IFN-gamma production playing a central role in protection to liver stage malaria (38). The thrombospondin-related adhesion protein (TRAP) is an antigen expressed on the sporozoites which has previously been shown to induce a protective CD8⁺ T cell responses (39). TRAP has been extensively tested in vaccine clinical trials as a fusion protein with a multiepitope string containing additional B-cell, CD8⁺ and CD4⁺ T cell epitopes, known as ME.TRAP (40,41). In humans, FP9-MVA.ME.TRAP prime-boost regimes have been shown to induce CD8⁺ as well as CD4⁺ T cell responses that conferred sterile protection in some volunteers (42,43). Adenoviral vectors of the human serotype 5 have previously been used in a P. yoelii mouse model of malaria and have shown outstanding immunogenicity and significant protection after just a single dose (44). However, one major limitation preventing the use of this serotype in humans is the ubiquitous presence of AdH5, with frequent childhood infections resulting in seroconversion. It has been reported that nearly all adults have antibodies against AdH5 (45), and 45% to 80% of individuals possess neutralizing antibodies (NAB) to the virus (46). To circumvent the problem of preexisting immunity to AdH5, there has been increased interest in the use of adenoviral serotypes of simian origin that do not circulate at appreciable levels in human populations, with a number of studies demonstrating the ability of these vectors to elicit CD8⁺ T-cell responses in both mice and nonhuman primate models of SARS (47) and HIV (48, 49).

In this current work, the inventors demonstrate for the first time in a mouse malaria model that with the use of a long intron A containing CMV promoter, as defined above, four simian adenoviral vectors, AdC6, AdC7, AdC9 (also known as C68 (50)), can induce outstanding CD8⁺ T cell responses often outperforming AdH5. Moreover, there was induction of high levels of sterile protection to a challenge with P. berghei after a single vaccination with the vectors. Finally, in conditions of preexisting immunity to AdH5 simian adenoviral vectors still maintained a high degree of protection which was abrogated with the use of human serotype 5.

2.1 Material and Methods

Mice and Immunizations

Female BALB/c mice 4 to 6 week of age were used and immunized intradermally, which has previously been shown to elicit better immunogenicity when compared to other routes e.g. sub-cutaneous, intramuscular (58). MVA.ME.TRAP (MVA) or FP9.ME.TRAP were administered at a dose of 1×10⁶ or 1×10⁷ pfu, and adenoviruses at a dose of 1×10⁹ or 1×10¹⁰ viral particles (v.p.).

Viral Vectors

All vectors express the transgene ME.TRAP that has been previously described (40,71). The insert ME.TRAP is a hybrid transgene of 2398 bp encoding a protein of 789 aa. The ME string contains the BALB/c H-2K^(d) epitope Pb9 amongst a number of other B- and T-cell epitopes (72). The simian adenoviral vectors (SAdV) and the AdHu5 vector were constructed with a intron A bearing long CMV promoted as described (73). Construction of the MVA (71) and FP9 (43) has been described earlier.

Ex Vivo IFNγ ELISPOT

ACK-treated splenocytes or PBMCs were cultured for 18-20 hours on IPVH-membrane plates (Millipore) with the immunodominant H-2K^(d)-restricted epitope Pb9 (SYIPSAEKI) at a final concentration of 1 μg/ml. ELISPOT was performed as previously described (74). To analyze the breadth of the immune response, splenocytes were stimulated with pools of 20-mer peptides overlapping by 10 aa spanning the entire length of TRAP (43,71) as well as a pool of peptides covering the ME string, all at a final concentration of 5 μg/ml.

Intracellular Cytokine Staining

ACK-treated splenocytes were incubated for 5 hours in presence of 1 μg/ml Pb9 and 4 μl/ml Golgi-Plug® (BD). Intracellular cytokine staining (ICS) was performed with BD cytofix/cytoperm Plus® kit according to the manufacturer's instructions. Splenocytes were stained with a suitable combination of fluorochrome-conjugated antibodies, specific for CD8 (clone 53-6.7, eBioscience), IFNγ (clone XMG1.2, eBioscience), CD27 (clone LG.7F9, eBioscience), CD43 (clone 1B11, BD/Pharmingen), CD127 (clone A7R34, eBioscience), IL-2 (clone JES6-5H4, eBioscience), mouse isotype controls IGg2a (eBR2a, eBioscience), CD16/CD32 Fcgamma III/II Receptor (2.4G2, BD/Pharmingen), anti-Granzyme B® (clone GB12, Caltag), IgG1 isotype control (Caltag). When CD62L (clone MEL-14, eBioscience) was used, stimulated cells were incubated with TAPI-2 peptide (Peptides International, USA) at a final concentration of 250 μM to prevent CD62L shedding from the cell surface. For peptide mapping and potency in C57BL/6 mice, splenocytes were stimulated with peptide pools containing 20-mers overlapping by 10, spanning all of the ME-TRAP sequence. The final concentration was 20 μg/ml. CD4 and CD8 responses were tracked by flow cytometry and individual peptides were synthesized after an analysis in the SYFPEITHI database to predict the immunodominant epitopes. Upon titration, individual peptides were used at a final concentration of 5 μg/ml.

Flow cytometric analyses were performed using a FACSCanto® (BD Biosciences) and data were analyzed with either FACSDiva® (BD) or Flow Jo® (Tree Star) software.

Evaluation of Antigen-Specific CD8⁺ T-Cell Response by Flow Cytometry

The frequency of IFNγ⁺ CD8⁺ T cells was calculated by subtracting the values from the unstimulated control, which never exceeded 0.1% in any of the experiments. The total number of antigen-specific cells was calculated as previously described (53). For the phenotypic makers investigated, each marker was compared to an isotype control.

ELISA

IgG antibodies against the TRAP region were analyzed by ELISA as described previously (43). For this experiment, serum was obtained from groups of at least 3 BALB/c mice after 2 weeks of immunization with individual vectors. Results were reported as a dilution factor needed for a sample in order to reach the O.D. of a naïve serum.

Parasite Challenge

Plasmodium berghei (ANKA strain clone 234) sporozoites (spz) were isolated from salivary glands of female Anopheles stephensi mosquitoes. Parasites were resuspended in RPMI-1640 medium with each mouse receiving a total of 1,000 spz via the i.v. route. Blood samples were taken on daily basis from day 5 to 20; smears were stained with Giemsa and screened for the presence of schizonts within the red blood cells. Survival was defined as complete absence of parasites in blood.

2.2 Results

Breadth of the Immune Response.

The breadth of the immune response to ME.TRAP was analyzed in BALB/c (FIG. 9 a) and in C57BL/6 (FIG. 10 a) mice by IFNγ ELISPOT. In BALB/c, the predominant response was directed towards the immunodominant H-2K^(d)-restricted epitope Pb9, whereas in C57BL/6 the response was present in three sub-pools: the ME string, TRAP 1 and TRAP 2. Additional analysis with intracellular cytokine staining and the use of SYFPEITHI database allowed the characterization of a CD4 epitope in TRAP 1 (IHLYVNVFSNNAKEI; SEQ ID NO: 9), a CD8 epitope in TRAP 2 (NVAFNRFLV; SEQ ID NO: 10) and a CD8 epitope in the ME string (DASKNKEKAL; SEQ ID NO: 11).

Kinetics of the Pb9-Specific CD8⁺ T Cell Response.

The CD8⁺ T cell response to Pb9 from all six vectors was investigated in terms of expansion, contraction and generation of memory cells. The simian adenovirus (SAds) AdC7 (C7), AdC9 (C9) elicited the strongest immune responses, followed by AdH5 (H5) (FIG. 9 b, 9 c, 9 d). Of the SAds, AdC6 (C6) was the least potent in terms of IFN-γ production but all Ads induced similar CD8⁺ T-cell expansion kinetics with a peak response about 20 days post-immunization. On the other hand, the poxviruses MVA and FP9 (which use a non-CMV poxvirus promoter) induced an immune response that peaked one week post vaccination, with a decrease in the frequency of CD8⁺IFN-γ⁺ cells observed as early as the 2 weeks post vaccination. The frequency of IFNγ⁺ CD8⁺ T cells at day 60 post-vaccination was highest in mice that were vaccinated with an adenovirus, this was most apparent in mice immunized with either C9 or H5. Thus, all adenoviral vectors share similar characteristics in terms of both strength and kinetics of the CD8⁺ T cell response, with profound differences in the expansion and contraction kinetics observed between adenoviral and poxviral vectors.

Effector CD8⁺ T-Cell Response.

Due to the short interval between infection and progression to disease, effector CD8⁺ T cells can play an important role in protection against malaria. Therefore, the acquisition of effector functions determined by the expression of a number of phenotypic markers, CD43 and Granzyme B, was investigated. CD43 expression has previously been shown to be upregulated during the effector phase of the CD8 response (51) while the cytolytic effector molecule Granzyme B (GrB), is highly expressed in CD8⁺ T effector cells, with lower levels observed in T_(EN) and T_(CM) (52), and it is one of the main mechanisms that CTLs use to kill infected cells. In general, adenoviral vectors induced a significantly higher percentage of CD8⁺IFN-gamma⁺CD43^(hi) over the entire course of the immune response when compared to the poxviral vectors. Interestingly, poxviral vectors induced a low percentage of CD43^(hi) as early as one week post-vaccination, suggesting a more rapid transition towards the memory phase especially with MVA. At day 60 post-prime, mice immunized with the adenoviral vectors still retained a significantly higher percentage of CD43^(hi) when compared to the poxviral counterpart (FIG. 11 a). In addition, levels of GrB were significantly lower in the MVA group at day 20 (p<0.001), and at day 60 both poxviral vectors were significantly lower than C6 (p<0.05) (FIG. 11 b, 11 c). These results demonstrate that in response to all four adenoviruses there was a full development of an effector response with preservation of cytolytic molecules for long periods of time, indicative of the presence of T_(EM) cells (52).

Functional and Phenotypic Memory Markers of Pb9-Specific CD8⁺ T Cells.

One of the main objectives of any vaccination regime is the generation of memory CD8⁺ T cells that are capable of persisting in vivo and expanding rapidly upon encounter with pathogens thus affording protection. To date a number of different molecules have been suggested to correspond to different sub-types of memory cells (53, 54). In this current study the inventors chose to investigate a number of these molecules to determine whether individual vectors induced different memory cells populations. During the early phase of the response, CD8⁺ IFN-γ⁺ cells generated in response to either FP9 or MVA displayed a CD62L^(hi), CD127^(hi) and produced IL-2, confirming the rapid transition towards a T_(CM) phenotype. Conversely, the adenoviral vectors did not induce a central memory CD8⁺ T phenotype, even by day 60, with the majority of CD8⁺IFN-γ⁺ cells displaying predominantly an effector memory phenotype (CD62L^(lo), CD127^(hi), and low percentage of IL-2 producing cells) (FIG. 12 a-d). Interestingly, CD27 remained low in mice vaccinated with adenoviral vectors, whereas the percentage of CD27⁺ cells increased over time in response to the poxviral vectors. Since CD8⁺ CD27⁻ cells are maintained in response to persistent antigenic stimulation (55), this may suggest that prolonged antigen stimulation was occurring in response to the adenoviruses. In summary, these results demonstrate that vaccination with adenoviral vectors induces predominantly a T_(EM) response, as evidenced by a CD62L^(lo), CD127⁺, IL-2^(low) phenotype in addition to the relative high percentage of CD43^(hi) cells as well as higher levels of cytolytic molecules 60 days post-prime.

Survival Following a Challenge with P. berghei.

To assess the level of protection afforded by these different vectors, mice were challenged with P. berghei as shown in Table 1. BALB/c mice were immunized with adenoviral (1×10¹⁰ vp) and poxviral vectors (1×10⁷ pfu) and then challenged 14 days (n=12) and 60 days later (n=6) by i.v. administration of 1000 sporozoites of Plasmodium berghei. Preexisting immunity to AdH5 was analyzed after injecting groups of 6 BALB/c mice with 5×10⁵ v.p. of AdH5 coding for an unrelated transgene (Ag85.A). 30 days later, the same mice were immunized with 1×10¹⁰ v.p. per mouse of AdH5, C6, C7 and C9 coding for ME.TRAP. Mice were challenged 14 days after the last immunization. Numbers represent the percentage of animals that survived the challenge. Statistical differences are indicated as: * p<0.05, ** p<0.01, *** p<0.001, and show comparison of individual regimes with the naïve control.

TABLE 1 Pre-existing immunity Day 14 Day 60 to H5 (day 14) (n = 12) (n = 6) (n = 6) Vector % % % H5 83 ***  0  0 C6 67 **  0 17 C7 83 *** 50 * 33 ** C9 92 *** 17 50 * MVA  0  0 n.t. FP9  0  0 n.t. Naive  0  0  0

In conditions with no previous immunity to AdH5 (day 14), C9 provided the best protection (92%), this was followed by C7, H5 (83%) and finally C6 (67%), all of them significantly higher than the naïve control group (0%, p<0.001). No protection was afforded by MVA or FP9 at the same time point. At day 60 post-prime, significant protection was achieved with C7 (50%) and C9 (17%) but no protection was observed when mice were immunised with either H5 or C6. The ability of these vectors to confer protection in presence of preexisting immunity to AdH5, which would mimic a human situation where at least 45% of the population is expected to have NABs to AdH5, was also assessed in this study. Mice were initially immunised with AdH5 containing an unrelated insert (Antigen 85A from Mycobacterium tuberculosis) which was followed 4 weeks later by the Ads vectors coding for ME.TRAP. In the presence of pre-existing AdH5 immunity, immunization with H5 gave no protection while C9 gave the best protection (50%), this was followed by C7 (33%) and C6 (17%). Both, C9 and C7 were significantly higher than H5 and the naïve controls (p<0.05 and p<0.01, respectively).

T-Cell Responses to Pf TRAP

To determine that immune responses are elicited by the P. falciparum TRAP within the ME-TRAP transgene, immunogenicity was analyzed by intracellular cytokine staining in splenocytes of C57BL/6 mice upon vaccination with all vectors. The ELISpot technique showed an immune response elicited by three sub-pools (FIG. 10 a). Flow cytometric analysis revealed the presence of one CD4 and one CD8 epitope in the TRAP sequence and a CD8 epitope in the ME string. Additional analysis using the SYFPEITHI database allowed the identification of the optimal peptide sequences for synthesis purposes (56). A similar trend in terms of potency of the CD4⁺- and CD8⁺-T cell responses was observed with respect to the Pb9 responses. C9 elicited the most potent TRAP T-cell responses, followed by C7, H5 and finally C6. Both poxviral vectors induced a more modest immune response measured on week 3 post-vaccination (FIG. 10 b).

Antibodies to TRAP

Induction of a TRAP-specific B-cell response by the vectors was assessed in sera from vaccinated mice. All of the adenoviral vectors were able to induce high levels of IgG antibodies against the TRAP region, whereas the poxviral vectors elicited low antibody levels. The strongest responses were achieved by AdH5 (O.D. x=3930±14), followed by AdC7 ( x=3358±256), AdC9 ( x=2862±979), AdC6 ( x=739±452); whereas MVA ( x=178±98) and FP9 ( x=126±95) induced minimal levels of antibodies (FIG. 13). Values for AdH5, AdC7 and AdC9 were significantly higher than the rest of the group.

2.3 Discussion

There is increasing evidence that T-cell responses may be a critical requirement for protection against diseases such as malaria, AIDS, tuberculosis and cancer. CD8⁺ T cells have previously been shown to play a central role in protection to the liver stage of malaria infection (57). A number of sub-unit vaccines, in the form of naked DNA and viral vectors, have been shown to induce strong CD8⁺ T cell responses in mice (44), providing protection against malaria.

Adenoviral vectors of the human serotype 5 (AdH5) have been tested in mice as vaccine candidates for a variety of infectious diseases (44, 58, 59). These vectors have displayed outstanding CD8⁺ T-cell immunogenicity in a prime-boost regime in combination with poxviral vectors and have conferred significant protection. However, in the only previous study of adenoviral vectors in the P. berghei model protection by homologous AdH5 immunization was minimal (58). Due to the ubiquitous presence of AdH5, a high percentage of humans develop antibodies that render the vaccine ineffective. To circumvent this problem, adenoviral vectors have been engineered from chimpanzee serotypes that do not circulate in humans. Previous studies have shown the ability of the chimpanzee adenovirus to elicit potent B- and CD8⁺ T-cell-mediated immune responses in models of rabies (50), SARS (47) and HIV (49), as a prime or heterologous prime-boost regimes in mice and primates.

The use of three chimpanzee adenoviral vectors, AdC6, AdC7 and AdC9 as a pre-erythrocytic malaria vaccine has been possible using an intron A bearing long promoter. The inventors have compared these vectors to AdH5 also expressing a long promoter and two poxviral vectors that have been widely used in human clinical trials, MVA and FP9.

The adenoviral vectors elicited the most potent CD8⁺ T cell responses, which peaked at week 3 yet maintained a high frequency of Pb9 specific cells even out to 60 days post-prime. In contrast, poxviral vectors peaked around the first week and then contracted rapidly. Upon analysis of a number of phenotypic markers, such as CD43 and GrB, Ads were shown to induce a potent effector population of cells which was significantly lower when mice were immunized with either of the poxviral vectors. In addition, MVA was shown to induce a lower level of GrB suggesting an overall reduced level of cytotolytic activity. Thus, adenoviral vectors were able to induce a sustained CD8⁺ T-cell effector response that was retained at high levels for at least 60 days after priming. Additional phenotypic markers showed that poxviral vectors induced the generation of a predominantly CD62L⁺, CD127⁺ CD8⁺ T cells, whereas the predominant phenotype of CD8⁺ T cells in response to the Ad vectors was CD62L^(dull/−), CD127⁺ over a long period of time. Based on expression of these markers, three different subsets of Ag-specific CD8⁺ T cells can be identified: effector T cells T_(E) (CD62L⁻CD127⁻); effector memory T cells T_(EM) (CD62L⁻CD127⁺) and central memory T cells T_(CM) (CD62L⁺CD127⁺) (60).

Antibodies to the TRAP region were also assessed after vaccination of BALB/c mice with each vector. Potency in terms of the B-cell response correlated well with the magnitude of CD8⁺ T cell responses. Protection against P. berghei in this system relies on CD8⁺ T-cell responses directed towards an immunodominant epitope, Pb9. Antibodies to TRAP would not play a role in protection due to the fact that the TRAP sequence is derived from P. falciparum. However, the presence of antibodies could add an extra benefit to improve protection in human infections with P. falciparum.

The inventors show that the simian adenoviral vectors using a long promoter elicited potent CD8⁺ T cell responses that are important in protection in a preerythrocytic mouse model of malaria. In contrast to rare human adenovirus serotypes, such as AdHu35 (70), the immunogenicity and efficacy of these simian vectors is as great or greater than AdH5. Comparison of the adenoviral vectors to two poxviral vectors, FP9 and MVA, demonstrated that the Ads were able to sustain a high number of CD8⁺ T cells over a long period of time that subsequently resulted in the generation of a high number of T_(EM) cells. Conversely, immunization with either of the poxviral vectors induced a high proportion of T_(CM) cells very early after immunization. In addition, all simian adenoviral vectors induced outstanding levels of protection during the effector phase of the response in absence and presence of preexisting immunity to AdH5, with protection being maintained for a long period of time with a number of the vectors. These data demonstrate for the first time that a single dose of a subunit vaccine is able to elicit protection to P. berghei and highlights the potential of the simian adenoviral vectors for a future application as a malaria vaccine in humans.

Example 3 Blood Stage Vaccines Against P. Falciparum Malaria

Based on the findings of Example 1 demonstrating the surprising ability of a Ad-MVA heterologous prime-boost immunisation regime to induce strong protective immunity to blood stage malaria in a P. yoelii murine malaria model, the inventors proceeded to generate adenovirus and MVA vectors encoding sequences from the MSP-1 gene of the human malaria parasite P. falciparum. This gene is dimorphic with two prevalence sequence types. It has a well studied block structure that allows the identification of conserved and variable blocks.

The PfM117 insert (see SEQ ID NO. 1) has been designed as a useful insert for immunisation. It comprises conserved sequence blocks 1, 3, 5 and 12 at the N terminus of a fusion protein followed by both copies of the important 33 kd fragment and at the C terminus of the protein the relatively conserved 19 Kd fragment. The 33 Kd fragment is a well studied immunogenic component of the MSP1 antigen that is known to contain T cell epitopes. It is however dimorphic with substantial sequence divergence between the two major types, often denoted by the labels Wellcome and MAD20 referring to the parasite strains that early sequences were derived from (Miller L. H. et al. Mol Biochem Parasitol. 1993, 59(1):1-14). In PfM117 the Wellcome strain sequence is found N-terminal to the MAD20 strain sequence, and immediately C-terminal to these is the 19 Kd sequence. This latter fragment is highly but not completely conserved amongst P. falciparum parasite strains and is known to be the target of protective antibodies. However some of these protective antibodies can be inhibited in their protective action by so called blocking antibodies (Uthaipaibul et al. J Mol Biol. 2001, 307 (5):1381-94.). Uthaipaibul et al. (2001) describe amino acid changes that can be made in the canonical sequence of the 19 Kd fragment that allow inhibitory antibodies to act preferentially over blocking antibodies, thereby increasing the likelihood that antibodies induced to this fragment should be protective. Therfore within this 19 Kd fragment three amino acids have been altered to avoid blocking antibody binding (Uthaipaibul et al. (2001)).

The PfM128 insert (see SEQ ID NO. 3), is identical to the PfM117 sequence with an additional copy of a 19 Kd fragment inserted between the two 33 Kd fragments. This additional 19 Kd fragment allows an alternative allelic sequence of that fragment to be expressed by this construct potentially broadening the range of protective antibodies or T cells that might be induced by PfM128 compared to PfM117.

We also constructed an additional insert “PfM115” that is very similar to the PfM117 sequence in that it comprises conserved sequence blocks 1, 3, 5 and 12 at the N terminus of the PfMSP1 fusion protein followed by both copies of the important 33 kd fragment and at the C terminus of the protein the relatively conserved 19 Kd fragment. However there are some minor sequences differences at the end of the 33 Kd fragments compared to the PfM117 corrected sequence. The PfM115 sequence was used to generate recombinant vectors of the C6, C7, C9 and AdHu5 serotypes (strain notation as in example 2) using again the intron A containing long promoter. Good vector genetic stability was observed. Potency as measured by antibody induction (FIG. 14) was excellent. In addition both CD4 and CD8 T cell responses were induced to peptide pools comprising the entire insert sequence of PfM115. Boosting with an MVA vector encoding the same insert led to enhanced antibody and T cell responses.

A widely used in vitro assay to predict the likely efficacy of blood stage vaccines against P. falciparum is the Growth Inhibitory Activity (GIA) assay (Bergmann-Leitner et al Am J Trop Med Hyg. 2006, 75:437-42; Malkin et al. Infect Immun. 2005, 73:3677-85.) This in vitro assay quantifies the % growth inhibition of blood-stage P. falciparum malaria parasites when cultured in the presence of test and control serum. A parasite enzymatic reaction is used to quantify parasite growth following the 40 hour time period of the assay. It is hoped that animals immunised with candidate blood-stage malaria vaccines will develop protective antibody responses. Serum from these animals can thus be screened using this assay for their ability to inhibit parasite growth. Considerable efforts have been made to standardise this assay, particularly by the NIH laboratory of C. Long. Mice were immunised with the AdHu5-PfM115 insert and boosted with the corresponding MVA construct. Sera taken at a terminal bleed showed 46-52% GIA, as measured by the C. Long lab, a level that represents substantial inhibition of the growth of blood stage parasites (Bergmann-Leitner et al Am J Trop Med Hyg. 2006, 75:437-42). This result suggests that a corresponding immunisation regime used in humans will show protective efficacy.

To try to increase further the immunogenicity and likely protective efficacy of adenoviral vectored vaccines the AdHu5-PfM115 vectored vaccines was coadminstered as a mixture with the CpG sequence 1826 (Brunner et al. J Immunol. 2000, 165:6278-86). CpGs have been well studied as adjuvants for protein-based but not for vectored vaccines (Daubenberger C A, Current Opinion in Molecular Therapy 2007; 9:45-52). One previous study of a CpG sequence co-administered with an adenovirus vaccine encoding a tumour antigen PSA led to lower T cell immunogenicity than when administered without the CpG (Lubaroff et al. Vaccine 2006, 24:6155-62). However, coadministration of the 1826 CpG oligonucleotide with the AdHu5-PfM115 vaccine led to increased CD4 and CD8 T cell responses as measured by flow cytometry (FIG. 15). This suggests that coadministration of CpG oligonucleotides with certain viral vectors, including heterologous long promoter adenoviral vectors, may lead to enhanced T cell immunogenicity for a variety of antigenic inserts.

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The invention claimed is:
 1. A recombinant adenoviral vector comprising a promoter and at least one nucleic acid sequence encoding an antigen of a bacterial pathogen or a parasitic pathogen under the control of said promoter, wherein said promoter consists of SEQ ID NO: 7 and wherein said parasitic antigen is not a murine malaria parasite antigen.
 2. The adenoviral vector of claim 1, wherein said vector is replication deficient.
 3. The adenoviral vector of claim 1, wherein the adenoviral vector is the chimpanzee adenoviral vector AdC6 (C6), AdC7 (C7), or AdC9 (C9) vector.
 4. The adenoviral vector of claim 1, wherein the promoter excludes exon B of the cytomegalovirus immediate early 1 (CMV IE1) gene.
 5. The adenoviral vector of claim 1, wherein the parasitic antigen is a malaria antigen, which is not a murine malaria antigen.
 6. The adenoviral vector of claim 5, wherein the malaria antigen is a Plasmodium falciparum antigen.
 7. The adenoviral vector of claim 5, wherein the malaria antigen is a pre-erythrocytic malaria antigen or a blood stage malaria antigen.
 8. The adenoviral vector of claim 6, wherein the malaria antigen is selected from the group consisting of multi-epitope string-thrombospondin-related adhesion protein (ME-TRAP), circumsporozoite protein (CSP), and merozoite surface protein-1 (MSP-1).
 9. The adenoviral vector of claim 8, wherein the MSP-1 malaria antigen is PfM117 having the amino acid sequence of SEQ ID NO: 1, or PfM128 having the amino acid sequence of SEQ ID NO:
 3. 10. The adenoviral vector of claim 1, wherein the bacterial antigen is the Mycobacterium tuberculosis antigen 85A.
 11. An immunogenic composition comprising the adenoviral vector of claim 1 admixed with one or more pharmaceutically acceptable vehicles, carriers, diluents, or adjuvants.
 12. A composition or a kit comprising: (a) a priming composition comprising the adenoviral vector of claim 1 and (b) a boosting composition comprising a recombinant pox virus vector, said pox virus vector further comprising at least one nucleic acid sequence encoding an antigen from a bacterial pathogen or a parasitic pathogen which antigen is the same as the antigen in the priming composition.
 13. The composition or the kit of claim 12, wherein the promoter excludes exon B of the CMV IE1 gene.
 14. The composition or the kit of claim 12, wherein the parasitic antigen is a malaria antigen, which is not a murine malaria antigen.
 15. The composition or the kit of claim 14, wherein the malaria antigen is a Plasmodium falciparum antigen.
 16. The composition or the kit of claim 14, wherein the malaria antigen is selected from the group consisting of multi-epitope string-thrombospondin-related adhesion protein (ME-TRAP), circumsporozoite protein (CSP), and merozoite surface protein-1 (MSP-1).
 17. The composition or the kit of claim 16, wherein the MSP-1 malaria antigen is PfM117 having the amino acid sequence of SEQ ID NO: 1, or PfM128 having the amino acid sequence of SEQ ID NO:
 3. 18. A composition comprising the immunogenic composition of claim 11 and a CpG adjuvant.
 19. A method of eliciting an immune response to an antigen of a bacterial pathogen or a parasitic pathogen in a mammalian subject comprising administering to the subject an effective amount of the immunogenic composition of claim 11 sufficient to elicit the immune response to the antigen in said subject.
 20. A method of enhancing T cell immune responses to the immunogenic composition of claim 11 in a mammalian subject comprising administering said immunogenic composition in combination with a CpG adjuvant to said mammalian subject. 